The morbidity and mortality caused by essential hypertension (EH) represent major health care costs and concerns in the United States. Because the precursors of EH have their origins in childhood and adolescence, we have sought to identify risk factors for EH in populations at high genetic risk for the development of EH, i.e., blacks and children of hypertensive parents. A risk factor which has shown excellent promise is cardiovascular (CV) reactivity, the measures of the changes of hemodynamic variables, such as systolic and diastolic blood pressure, and heart rate in response to laboratory or natural life stressors. These stressors include: physical stress (exercise), psychological stress (video game challenge, star tracing), and "everyday life" stress (24 hour ambulatory blood pressure). Other markers, such as cardiac indices, especially left ventricular mass (LVM) and red blood cell sodium transport, have been shown to be linked directly with the development of CV diseases, such as coronary artery disease and EH. In our continued studies we seek to expand our initial investigations in a biracial population of healthy children who differ in genetic risk for EH, children of a hypertensive parent and children of normotensive parents. We seek to: I ) extend our preliminary study of 24 hour ABPM patterns; 2) establish the potential link between CV reactivity and echo-determined measures of cardiac dimensions and performance Indices, with emphasis on LVM - the most powerful risk factor presently known; 3) examine the importance of genetic influences on the above indices (CV reactivity and LV mass) by the study of siblings and unrelated pairs; 4) determine the prospective prognostic value of CV reactivity, 24 hour ABPM, and red cell sodium transport to predict blood pressure and LV mass after a 2 year follow-up, Findings from this continuation application studies should: I ) enhance the probability of designing a prospective screening and intervention program for the primary prevention of EH in adulthood; 2) expand current knowledge concerning risk factors for EH to allow further dissection into the mechanisms of EH in both white and black Americans.